RNA & Protein Synthesis Vocabulary: Messenger RNA (mRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA) Transcription Polymerase Promoter Intron Exon Codon Translation Anticodon Key Concepts: What are the 3 main types of RNA? What is transcription? What is translation?

The Importance of Proteins Proteins are diverse! They control chemical messages in cell Direct the synthesis of carbohydrates, lipids, and nucleotides Act as enzymes Give the cell structure and movement

RNA Like DNA= made of nucleotides Disposable copy of DNA segment 3 differences: 1) sugar= ribose 2) single stranded 3) instead of the base thymine (T), RNA uses uracil (U)

RNA 3 types: mRNA – used in transcription tRNA – used in translation rRNA – component of ribosome

Info about Transcription Step #1 (of 2) of protein synthesis Transcribe: to make a copy Starts in the nucleus Uses 1 side of DNA as a template Copies 1 gene at a time Makes a section of mRNA

Transcription transcribing DNA information (gene instructions) into mRNA which can leave the nucleus and go to the ribosomes in the cytoplasm messenger RNA= mRNA (1 type of RNA) special base sequences in DNA are recognized by RNA as “start” and “stop” signals “Start” sequence called promoter region of DNA

Details of the Process 1.RNA polymerase attaches to DNA and it separates the 2 DNA strands (unzips the strand)

2. RNA polymerase synthesizes the mRNA strand using complimentary base-pairing

Remember…there aren’t “T” bases in RNA “C” binds with “G” DNA “A” binds with RNA “U”

Which strand was copied? A or B

3. when RNA polymerase reaches the end or "STOP" part of the genetic code for that protein, it releases 4. DNA re-zips   5. finished mRNA (messenger) leaves the nucleus and goes to a ribosome in the cytoplasm

mRNA bases are grouped by 3 Each group of 3 nucleotides are called a codon (“code”)

Review of Transcription Base pair rule is still used but there is never any thymine in RNA so: (A-U & C-G). Uracil is the base that bonds with adenine. DNA can never leave the nucleus, so mRNA serves as the messenger to the ribosome RNA has one strand while DNA has 2. mRNA leaves the nucleus and travels to the ribosome to start Translation.

More Review of Transcription Transcription occurs in the nucleus The product of transcription is mRNA Only 1 side of DNA is used as a template & only 1 gene is needed Enzymes regulate the process

Transcription ends with mRNA which will exit the nucleus to the cytoplasm So… if Transcription is the first step of Protein Synthesis, what happens next in the cytoplasm?

Transcription Translation

TRANSLATION Making a protein (string of amino acids) from the information carried by mRNA. Occurs in the ribosome. A group of 3 mRNA bases makes up a “codon” (think of as a “code word”) each codon specifies a particular amino acid there are “start” and “stop” codons

Quick Review of Proteins Made of amino acids There are only 20 amino acids to make up a lot of proteins Proteins are a major component of cells Proteins are made in ribosomes

tRNA Amino acid tRNA anticodon mRNA codon

The Mechanism... 3 nucleotides of mRNA = codon mRNA travels from the nucleus and attaches onto the ribosome with codons 3 nucleotides of mRNA = codon 2nd kind of RNA= ribosomal RNA (rRNA) makes up the majority of the ribosome

The Mechanism continued... 3rd kind of RNA= transfer RNA (tRNA) carries amino acids to the ribosomes (amino acids join together to form proteins) there are 64 different tRNA molecules (more than 1 for each amino acid) REDUNDANCY of the CODE!! 3 nucleotides of tRNA that “match” or compliment the mRNA = anticodon

amino acid tRNA anticodon codon (mRNA)

The Mechanism continued... By matching the codon of mRNA to the anticodon of tRNA, the correct amino acid is put into place, then tRNA releases and leaves the amino acid in place. Next tRNA goes here!!!!

The genetic code …is universal …is a correlation between the codon on mRNA and an amino acid …some amino acids have more than one codon …there are stop & start codons

The Genetic code Third letter

The Mechanism continued... a peptide (covalent) bond is formed between the 2 amino acids

The Mechanism continued... protein chain continues to grow until a “stop” codon is reached on the mRNA no tRNA exists for “stop” codons

The end of the Mechanism... the protein is now finished & released!!

Translation: All At Once

PROTEIN SYNTHESIS: All At Once

PROTEIN SYNTHESIS DNA Step 1. TRANSCIPTION (nucleus) mRNA Step 2. TRANSLATION (ribosome) tRNA PROTEIN

Protein Synthesis: the whole process

Review of Translation Purpose is to make bring amino acids to the ribosomes to make proteins. Translation occurs on the ribosomes as tRNA delivers amino acids. This occurs as the anticodons on the tRNA match up with the codons of the mRNA. A start codon begins the process. Once the amino acids are delivered the tRNA leaves and gathers more. The stop codon ends the process and the amino acid chain makes a protein.